Electrical musical system



June 26, 1962 c. J. TENNES ELECTRICAL MUSICAL SYSTEM 2 Sheets-Sheet 1 Filed July 3, 1958 FIG. l

Key

Oscillator INVENTOR. Char/es J, 7nnes June 26, 1962 c. J. TENNES 3,040,613

L ELECTRICAL MUSICAL SYSTEM Filed July s, 195:3 2 sheets-sheet 2 *l Tramo/o 4504200/ Organ Voice Generdor Ph/z/gfW/ff Mixer 8914 rd/6l 89 79 Moduldfor 3 63 Channel B Manud/ #l /\NW F/ues 8 Srngs 547 Only Express/0n l @man 627 Channel A. Amp//f/'er Md/n Preamp//fler 8 Expression Conro/ INVENTOR. Char/es J ennes United States Patent O 3,040,613 ELECTRICAL MUSICAL SYSTEM Charles J. Tenues, Elkhart, Ind., assignor to C. G. Conn, Ltd., Elkhart, Ind., a corporation of Indiana Filed July 3, 1958, Ser. No. 746,432 11 Claims. (Cl. 84-1.25)

This invention relates to electrical musical instruments and more particularly to apparatus for providing a controlled tremolo effect at the sound output of such instruments.

The production of tremolo or similar undulating effects is desirable in the playing of various musical instruments Including electric organs. In some electric organs, trem- Jlo is provided by a built-in generator to cause frequency modulation of the various tone producing oscillators of the organ. While this method has generally proved satisfactory in producing the amount of tremolo generally required in the rendition of classical and church music, the playing of most popular music requires the use of a more pronounced tremolo effect than can conveniently be produced in this way.

In an electric organ, it is also desirable to provide means for varying the amount of tremolo impressed upon the different voices of the instrument, the most pronounced tremolo generally being impressed on the flute family of voices. Such variation in tremolo effect has been diflcult to produce using conventional built-in tremolo generators.

It has also been proposed to create tremolo effects by moving a sound transmitting channel at a controlled rate, such as by rotating a loudspeaker. However, such arrangements have proved undesirably complicated and expensive. In addition, mechanical tremolo impressing devices cannot be stopped or started instantaneously because of inertia of the moving parts.

It is an object of the present invention to provide an effective yet relatively simple and inexpensive tremolo producing means for .electrical musical instruments such as organs. Y Y

It is another object of the invention to provide means for impressing a relatively large amount of tremulant, such as the amount of tremulant appropriate to the playing of popular music, to the sound output of an electric organ.

lt is a further object of the invention to provide an improved tremolo system for an electric organ wherein the amounts of tremolo and the. voice tones of the electric organ on which the tremolo is impressed are controlled.

A feature of the invention is the provision of an audio output system for an electronic organ including a primary tone emitting speaker and a modulating speaker which emits va tone signal periodically varied at a tremulant frequency, yso that it modulates the output thereof Aand results in a cyclic variation in the sound wave resulting from both speakers. The modulating speaker may be mounted so that sound therefrom is only indirectly radiated to listeners but combines with the sound from the primary speaker to provide an overall tremolo effect. In some embodiments of the invention, a plurality of modulating speakers may be used which provide tremolo outputs having difference phases. Y Another feature of the invention is the provision of a primary speaker emitting a normal audio signal and a modulating electro-magnetic speaker emitting a modulated signal which is produced by the application of an alternating current of relatively low frequency to the field coil of the modulated speaker thus cyclically modulating the tone signal impressed on'the voice coil.

Still another feature of the invention is the provision of an amplifier with voltage amplifier tubes connected to a low frequency alternating current source and further having its output connected t-o the field coil of ICC a loudspeaker which is bridged by a capacitor, so that the coil and capacitor will resonate at the aforesaid low frequency thus providing for maximum efficiency with minimum power and effectively modulating the signal from the loudspeaker.

A further feature of the invention is a two speaker system in which the output of one of the speakers is modulated by cyclically reversing the polarity of a tone signal applied to a voice coil. The simultaneous sounding of an unmodulated tone of the same frequency from the other speaker results in the production of a sound having a pleasing tremolo effect.

In the accompanying drawings:

FIG. l is a block diagram showing the essential parts of a tremolo producing system in -accordance with one embodiment of the invention;

FIG, 2 is a schematic diagram showing the power amplifier means for periodically interrupting a tone signal on the voice coil of a loudspeaker;

FIG. 3 is a block diagram showing a tremolo producing system in accordance with -another embodiment of the invention;

FIG. 4 is a schematic diagram of a modulator circuit useful in connection with the system of FIG. 3;

FIG. 5 illustrates, in somewhat diagrammatic form, the placement of speakers in an electric organ utilizing the invention; and

FIG: 6 illustrates a placement of loudspeakers in a separate cabinet used in connection withinstruments employing certain embodiments of the invention.

In accordance with the present invention, an electrical musical instrument such as an electric organ is provided with a primary speaker and a modulated electro-magnetic speaker. While a normal or untremulated tone signal is applied to the primary speaker, the same signal and a low frequency tremulant signal are applied to the modulated speaker in such a way that the output of the modulated speaker is periodically interrupted and the resultant sound from both speakers has a desirablek tremolo effect. Signal interruption in the modulated speaker may take place by applying a normal tone signal to the voice coil of an electro-magnetic speaker and a low frequency alternating current to the eld coil thereof. Alternatively, the tremolo effect can be provided by periodically cutting off the primary tone signal applied to the voice coil of the speaker. The provision of at least a pair of speakers provides a desirable largeness of the sound in addition to producing the tremolo. The amount of tremolo can be controlled by directing more or less of' various parts of the complete organ signal through the modulated speaker.

The system illustrated diagrammatically in FIG. l shows a primary electro-magnetic speaker 10 having a voice coil 11 and a field magnet 12 together with a modulated speaker 13 having a voice coil 14, a magnetic field structure =16, and a field coil 17. The primary organ tone signal is supplied to the voice coils 11 and 14 from the tone oscillator 18 through the action of the key i191 The oscillator 18 may provide both flute andl string type tones which may be combined to provide desired organ voices in circuits controlled by the organ stops indicated at 22. The signal is amplified through the power amplifier 24. The primary speaker 10 may be any device operative to translate electrical tone signals into sound waves.

In Vthe system illustrated in FIG. l, a tremolo output is provided by cyclically reversing the magnetic field in the loudspeaker field structure 16 by reversal of the voltage in coil 17. "Ihis is done by providing ya tremulant signal at a low frequency from the source 26. The tremolo `oscillator 26 may be any convenient means for generat- 'ing a low frequency alternating current usually having the frequency between about 3 and 20 cycles per second.

The output from the tremolo oscillator 26 is controlled through the tremolo stops indicated at 27 and is amplified through the power amplifier stage 28.

The power amplifier 2.8 is illustrated in FIG. 2. The tremolo alternating current signal Iis applied at input connection 31 to level control potentiometer 32 and is amplified by the triodes'33 and 34 which are coupled through the capacitor 36. The triode 33 has its cathode grounded through resistor 37 and its plate connected to B+ potential through load resistor 38. The triode 34 has its plate connected to B+ through the load resistor 41, with resistor 42 providing a grid return, resistor 43 providing cathode bias. Resistors 42 and 43 are in turn connected to ground through the load resistor 44.

The circuit further includes a push-pull output amplifier made up of the triodes 511 and 52. The output of triode 34' is coupled through the capacitors 46 and 47 across a voltage divider made up of resistors 48 and 49 to the grids of the triodes 51 and 52. A balancing resistor 53 is connected to the cathodes of tubes 51 and 52 with its movable tap grounded through the parallel connected capacitor 54 and resistor 56. The coil 17 is connected to the anodes of the triodes 51 and 52 and is provided with a center tap S connected to a positive voltage source to apply B+ potential to the triodes.

The output of the power amplifier is applied to the input terminals of the field coil 17. A capacitor 57 is connected across the coil 17 and tunes the coil to provide a tank circuit resonating at the frequency of the tremolo input signal applied at 31. This provides maximum efliciency of the system so that a minimum amount of power is required.

The periodic reversing of the lcurrent through the field coil 17 causes a corresponding reversal of theV field in the structure 16 and thus periodically interrupts the output "of the speaker 13 which has a tone signal applied to the voice coil 14. The sound produced by the modulating speaker 13 is thus one which rises in amplitude, falls to zero, and then rises and falls to zero with the opposite polarity. The signal components thus change polarity every half cycle. The change in polarity makes no change in the sound but each half cycle in the field produces a full cycle of the sound to effectively double the frequency of the tremolo input signal. When this sound is combined with the normal organ tone derived from the primary speaker 10, a pleasing tremolo effect is obtained.

Although the system illustrated in FIG. l shows a single primary speaker and a single modulated speaker, it will be understood that a plurality of modulated speakers may be used to which the tremolo signal is applied in matching or displaced phase. Also, a plurality of unmodulated signal speakers may be used. It may also be desirable to apply only a part of the organ tones through the modulated speaker such as the flute tones.

FIG. 3 is Ia block diagram illustrating an embodiment of the invention wherein a modulated tone signalV is obtained by periodically interrupting the current actuating the voice coil of an electro-magnetic speaker. Although the embodiment particularly illustrated shows two modulated speakers and two primary speakers it will be understood thatthe same principles described may be applied to systems containing more or less modulated or primary speakers.

The output of an organ voice mixer indicated at 61 is divided into a first channel 62 and a second channel 63 with the latter being for flute and string voices which are to be more heavily tremulated. The output of either channel is delivered to the organ amplifier 64 and hence to the Voice coils 66 and 67 of speakers 68 and 69 respectively. These are the primary speakers which deliver an untremulated tone. As in the system illustrated in FIG. l, 4they may be any device :operative to translate electrical tone signals into sound waves. The output of the second channel 63 also passes to the modulators indicated at 71 and 72 which are illustrated in more detail in FIG. 4. The output of the modulators is delivered to the voice coils 73 and 74 of speakers 76 and 77 respectively to produce a modulated signal as will be explained subsequently. A tremolo generator 77 delivers a low frequency alternating current input to each of the modulators 71 and 72 with a phase shift network 78 provided between the generator 77 and the modulator 71 so that there may be a phase difference between the modulated outputs of speakers 76 and 77 if desired.

FIG. 4 is a schematic diagram of the circuit employed in modulators 71 and 712. An organ signal input is applied at the terminal 79 which is connected to the grid of an amplifying triode I811. The output of triode 81 is coupled to the grid of phase-splitting triode 82 through capacitor 83 and across signal amplitude or volume control resistor 84. The output from the plate of the triode 82 is applied across input resistors 85 and 86 and fed to the grid of amplifier triode 87 which forms a pushpull amplifier section with triode 88. The out of phase output from the cathode of amplifier 82 is applied across resistors 103 and 104 to the grid of triode `88. A balancing resistor is connected between the cathode of triodes 87 and 88 and has a movable tap connected to ground.

The tremolo input at 89 is connected to the grid of the phase-splitter triode 91 through tremolo amplitude control resistor 92 and capacitor 93 and across the resistors 101 and 102. The plate of triode 91 is connected to a point between resistors 85 and 86. The output from thel cathode of triode 91 is coupled to a point between resistors 103 `and 104. The modulated output of the push-pull amplifier section is coupled to the grid of amplifier 94 through a filter network composed of capacitors 96 and resistors 97. The output of the triode 94 is connected to the voice coil 74 of the speaker 77.

The low frequency signal applied at terminal 89 serves to alternately bias triodes 87 and 88 to cut off thus permitting the tubes 87 and 88 to alternately conduct. Accordingly, the signal applied to the triode 94 is cyclically interrupted so that the signal on the voice coil 74 rises in amplitude in one direction, falls to zero, reverses polarity instantaneously and rises and falls to zero at this negative polarity in essentially sinusoidal manner. A modulated output is provided by speaker 77 as well as by speaker 76 which is connected to an identical modulator 71. The result of these two modulated outputs with the primary unmodulated outputs of speakers 68 and 69 re` sults in -a pleasing tremolo effect. The phase shift network 78 may be used to modulate the outputs of speakers 76 and 77 so that there is a phase difference between them `thus producing a variety of undulating tone effects.

It may be desired to provide filter means for the tone signal applied to the modulating speaker in order to attenuate a particular frequency range. For example, a series capacitor may be used to sum the signal for the Vmodulating speaker so that lower frequency signals are less effectively translated. Such filter means may be provided in connection with any of the embodiments described herein.

FIGS. 5 and 6 illustrate two ways in which the primary speakers and modulating speakers of the systems aforesaid may .be used in connection with electric organs. FIG. 5 shows an electric organ generally indicated at 150 and including a grill. 151 behind which are mounted a plurality of primary speakers 152. The speakers may be generally the same as the primary speaker 10 illustrated in FIG. 1 or the primary speakers `68 and 69 illustrated in FIG. 3. Y Y

The organ is provided with an expression pedal 153 extending into the recessed housing 154. A modulating speaker 156 is positioned at the top of the housing 154 so that its output is directed along a line essentially perpendicular to the output of the primary speakers 151 and Y [52. 'Ihe speaker 156 may be either the field coil modated type such as the speaker 13 shown in FIG. l or the voice coil modulated type such as the speakers 76 and 77 ihown in FIG. 3.

4Because of the pronounced undulating nature of the sound signal emitted by the modulated speaker, it is pre- Eerred to so arrange the speakers that the output of the modulated speaker will not reach the listener in undulated form but will be masked and heard only as combined with the sound from the primary speaker. It has been found that substantial improvement in the tone qualities of the instrument are obtained by mounting the modulating speaker 156 with its sound producing axis i.e., the axis of the speaker cone, yat right angles to the sound producing aixs of the primary speakers and this may be done in the embodiment shown in FIG. 5 either by mounting it at the top or at the sides of the housing 154. The axis of the modulating speaker does not point directly at the listener. The housing 154 provides a desirable 4baffling effect. Alternatively, the cone of the modulating speakers may be mounted concentric within the cone of the primary speaker to provide suitable sound mixing and in such an arrangement may point directly toward the listener.

FIG. 6 illustrates a separate speaker cabinet 160 which may be used in connection with an electric organ or other instrument embodying the principles of the present invention. Here, primary electromagnetic speakers 161 and 162 are positioned behind the grill 163 of the cabinet while the modulated speaker 164 is positioned at the bottom of the cabinet with its sound producing axis perpendicular to the surface supporting the cabinet. As in the embodiment shown in FIG. 4, the outputs of the primary and modulated speakers are thus at right angles to one -another and the output of the modulated speaker is not projected directly toward the listener. Again, the mod ulated speaker 164 may be of either the field coil or the voice coilr modulated variety.

rIhe invention thus provides a particularly effective and relatively inexpensive tremolo producing system particularly useful in electric organs, although it is applicable to any musical instrument in which the tone can be derived from an electric signal. The use of at least two speakers, one emitting a primary signal and the other emitting a modulated signal, provides for a desirably large sound in organs. By providing for the production of a tremulated signal by either the modulation of the field coil or the voice coil of an electro-magnetic speaker, a greater amount of tremulant can be obtained than was heretofore Iavailable by conventional means. This system has substantial advantages over mechanical methods for producing tremolo since it can be started or stopped instantaneously and since it is substantially less expensive.

I claim:

l. An electrical musical instrument including in combination, first means for providing electrical tone signals representing musical notes, second means coupled to said first means for translating said tone signals into first sound waves, third means for providing an alternating current signal of a frequency substantially below the frequency of said tone signals, and fourth means coupled to said first and third means responsive to said alternating current signal for modulating said tone signals to provide signals which rise, fall and reverse in a sinusoidal manner and for translating the modulated signals into second sound waves, said second and fourth translating means being positioned adjacent to each other so that said first and second sound Waves emanating therefrom combine to provide a tremolo effect.

2. An electrical musical instrument including in combination, first means for providing electrical tone signals representing musical notes, second means coupled to said first means operative to translate said tone signals into a first sound signal, an electro-magnetic speaker comprising a field magnet and a voice coil, a field coil controlling the magnetic field in said field magnet, means for apply# ing a relatively low frequency alternating current signal to said field coil for cyclically reversing the polarity of its magnetic field, and means coupled to said first means for applying the aforesaid tone signal to said voice coil, said voice coil being responsive to said magnetic field to provide a modulated second sound signal, said second means and said loudspeaker being positioned adjacent each other so that the sound signals emanating therefrom combine to provide a tremolo effect.

3. .An electrical musical instrument including in combination, means for providing electrical tone signals representing musical notes, first speaker means operative to translate said tone signals into first sound waves including first voice coil means, means for applying said tone signals to said rst voice coil means, second speaker means including second voice coil means, means for modulating the aforesaid tone signals by a relatively low frequency sinusoidal alternating current signal to provide a signal which rises, falls and reverses in a sinusoidal manner, and means for applying the modu- .lated signals to said second voice coil means, said first and second speaker meanskbeing positioned adjacent to each other so that said rst and second sound waves are combined to provide a tremolo effect.

4. An electrical musical instrument including in cornbination, primary loudspeaker means, a plurality of modulated electro-magnetic speaker means, means for applying a tone signal simultaneously to said primary speaker means and said modulated speaker means, means for generating a relatively low frequency alternating current, and a phase shifting network coupled to said generator means for applying said alternating current as separate phase displaced signals to said modulated speaker means, said modulated speaker means providing signals which rise, fall and reverse in a sinusoidal manner, said loudspeaker means and said speaker means being positioned adjacent to each other so that the sound therefrom is combined to provide a tremolo elect.

5. Apparatus for providing a modulated tone including in combination, an electro-magnetic speaker having a voice coil, -a field magnet and a field coil, means for supplying a relatively low frequency alternating current, an amplifier circuit having output terminals connected to said field coil, an input terminal coupled to said low frequency alternating current means, said amplifier circuit including a pair of voltage amplifier tubes connected in push-pull between the output terminals of said circuit, a capacitor connected in parallel with said coil and adapted to tune said field coil so that said coil and said capacitor resonate at the frequency of the alternating current applied thereto, and means for applying a musical tone signal to said voice coil.

6. An electrical musical instrument including in combination, a first electro-magnetic speaker having a voice coil, a field magnet and a field coil, means for supplying a relatively low frequency alternating current, an amplifier circuit having output terminals connected to said field coil, an input terminal coupled to said low frequency alternating current means, said amplifier circuit including a pair of voltage amplifier tubes connected in push-pull between the output terminals of said circuit, a capacitor connected in parallel with said. coil and adapted to resonate with said field coil at the frequency of the alternating current applied at said source, means for applying a musical tone signal to said voice coil to produce first sound waves, and separate means positioned 'adjacent said speaker for translating said tone generating signal to second sound Waves, with said first and second sound waves mixing to provide a tremolo effect.

7. An electrical musical instrument including in cornbination, first means for providing electrical tone signals representing musical notes, a first loudspeaker coupled to said first means for translating said tone signals into first sound waves, second means for providing an alternating current signal of a frequency substantially below the frequency of said tone signals, means coupled to said `first and second means and including a second loudspeaker responsive to said alternating current signal for modulating said tone signals to provide signals which rise, fall and reverse in a sinusoidal manner and for translating the modulated signals into second sound Waves, said second loudspeaker being mounted with its sound emitting axis angularly disposed with respect to the sound emitting axis of said rst loudspeaker with said first and second sound waves emanating from said loudspeakers combining to provide a tremolo effect.

8. 'Ihe combination according to claim 7 wherein the sound emitting axis of said first loudspeaker is directed toward the front of said instrument, and the sound emitting axis of said second loudspeaker is directed downwardly in a direction substantially perpendicular to the sound emitting axis of said first loudspeaker.

9. An electrical musical instrument including in combination, means for providing electrical tone signals representing musical notes, first loudspeaker means coupled to said tone signal means for translating said tone signals into first sound waves, means for providing an alternating current signal of a frequency substantially below the frequency of said tone signals, means including second loudspeaker means coupled to said tone signal means and to said alternating signal means and responsive to said alternating current signal for modulating said tone signals to provide signals which rise, fall and reverse in a sinusoidal manner and for translating the modulated signals into second sound waves, with said first and second loudspeaker means being positioned relatively to one another to produce a combined sound Wave signal tending to mask said second sound waves.

l0. Apparatus for providing a modulated sound signal including in combination, first means for translating electrical signals representing -musical notes to provide first sound waves, second means for providing a relatively low frequency electrical signal, means coupled to said second means for modulating electrical signals representing musical notes by said low frequency signal to provide modulated electrical signals which rise, fall and reverse in a sinusoidal manner, a speaker operative to translate said modulated electrical signals into second sound Waves, said speaker comprising a magnetic structure and a voice coil, and means for applying said modulated electrical signals to said voice coil, said first means and said speaker means being positioned adjacent to each other so that said first and second sound waves are combined.

11. Apparatus for providing a modulated sound signal including in combination, means for translating musical signals representing musical notes to provide first sound Waves, a speaker operativeto translate electrical signals to provide second sound Waves, said speaker including a iield magnet and a voiced coil, said field magnet including a coil controlling the magnetic field in said field magnet, means for applying a relatively low frequency alternating current signal to said coil for cyclically reversing the polarity of said magnetic field of said field magnets, and means for applying tone signals representing musical notes to said voice coil of said speaker, said first named means and said speaker being positioned `adjacent each other so that said rst and second sound waves provide a combined effect.

References Cited in the file of this patent UNITED STATES PATENTS 1,866,090 De Forest July 5, 1932 1,988,250 Olson a Jan. 15, 1935 2,114,680 Goldsmith Apr. 19, 1938 2,310,429 Hanert Feb. 9, 1943 2,466,306 Daniel Apr. 5, 1949, 2,534,342 Daniel Dec. 14, 1950 2,542,065 Van Wye Feb. 20, 1951 2,548,235 Olson Apr. 10, 1951 2,533,566 Hanert Ian. 29, 1952 2,817,708 Fender Dec. 24, 1957 2,872,516 Hoffman Feb. 3, 1959 

